The present invention relates to a piston type compressor used in, for example, a vehicle air conditioner and a compressor assembly method.
A conventional variable displacement swash plate type compressor shown in FIG. 7 includes an electromagnetic clutch 101 between a drive shaft 104 and a vehicle engine Eg, which is an external driving source. The electromagnetic clutch 101 includes a rotor 101b connected to the engine Eg and an armature 101a integrally, rotatably secured to the drive shaft 104. When the electromagnetic clutch 101 is turned on, the armature 101a is pulled toward the rotor 101b and engages the rotor 101b, which engages the clutch 101. Accordingly, the power of the engine Eg is transmitted to the drive shaft 104. When the electromagnetic clutch 101 is turned off, the armature 101a is moved away from the rotor 101b, which disengages the clutch 101. Accordingly, the drive shaft 104 is disconnected from the engine Eg.
A rotor 105 is fixed to the drive shaft 104 in a crank chamber 107. A thrust bearing 111 is located between the rotor 105 and a housing 110. A swash plate 103 is connected, through a hinge mechanism 106, to the rotor 105. The swash plate 103 is supported on the drive shaft 104 and inclines with respect to the axis L. The swash plate 103 is driven integrally with the drive shaft 104 through the hinge mechanism 106. A restriction ring 109 is provided on the drive shaft 104. When the swash plate 103 contacts the restriction ring 109, the swash plate 103 is defined at the minimum inclination angle position.
A cylinder bore 108 is formed in the housing 110. A piston 102 is accommodated in the cylinder bore 108 and is connected to the swash plate 103.
The inclination angle of the swash plate 103 is changed by changing the difference between the pressure in the crank chamber 107 and the pressure in the cylinder bore 108 through the piston 102. Thus, when the inclination angle is changed, the stroke of the piston 102 is changed so that the discharge displacement is changed.
When the inner pressure of the crank chamber 107 is increased and the difference between the increased pressure in the crank chamber 107 and the pressure in the cylinder bore 108 becomes large, the inclination angle of the swash plate 103 decreases and the discharge displacement of the compressor becomes small. A broken line in FIG. 7 shows the swash plate 103 at the minimum inclination angle position, where it contacts the restriction ring 109. On the other hand, when the inner pressure of the crank chamber 107 is decreased and the difference between the decreased pressure in the crank chamber 107 and the pressure in the cylinder bore 108 becomes small, the inclination angle of the swash plate 103 increases and the discharge displacement of the compressor becomes large. As a result, the swash plate 103 is moved to the maximum inclination angle position.
When refrigerant gas is being compressed, and in particular, when the swash plate 103 is at the maximum inclination angle position, a strong compression load force is transmitted through the piston 102, the swash plate 103, the hinge mechanism 106, the rotor 105 and the drive shaft 104 to the inner wall surface of the housing 110.
When the electromagnetic clutch 101 is turned off, or when the engine Eg is stopped, the pressure in the crank chamber 107 is increased and the swash plate 103 is moved to the minimum inclination angle position. As a result, the compressor is stopped in a state where the inclination angle of the swash plate 103 is minimum, in other words, in a state where the discharge displacement is minimum. Therefore, the compressor is always started from the minimum discharge displacement, where the load torque is minimum. This reduces the shock generated when the compressor is started. In addition, when a vehicle is abruptly accelerated, the load on the engine Eg is reduced. Thus, the pressure in the crank chamber abruptly increases so that the discharge displacement of the compressor becomes minimum.
However, when the pressure in the crank chamber 107 is abruptly increased, the inclination angle of the swash plate 103 is rapidly reduced. Accordingly, the swash plate 103 (as shown by the broken line in FIG. 7) moves to the minimum inclination angle position and strongly presses against the restriction ring 109. Further, the swash plate 103 pulls the rotor 105 rearward (in the right direction of FIG. 7) through the hinge mechanism 106. As a result, the drive shaft 104 is moved axially rearward against the force of a support spring 113.
When the drive shaft 104 is moved in the rear direction when the compressor is stopped by disengagement of the electromagnetic clutch 101, the armature 101a, which is secured to the drive shaft 104, is moved toward the rotor 101b. This may eliminate the clearance between the armature 101a and the rotor 101b, and the armature 101a may contact the rotor 101b, which is rotating. As a result, noise or vibration occurs, or, in spite of the deactivation of the clutch 101, the power of the engine Eg may be transmitted to the drive shaft 104.
When the drive shaft 104 is moved rearward, the piston 102, which is connected to the drive shaft 104 through the rotor 105, the hinge mechanism 106, and the swash plate 103 are also moved rearward. Thus, the top dead center position of the piston 102 is moved toward a valve plate 112. Accordingly, the piston, which reciprocates in the cylinder bore 108, may repeatedly collide with the valve plate 112. As a result, vibration or noise occurs.
To prevent the movement of the drive shaft 104 in the rearward direction, increasing the force applied by the supporting spring 113 has been considered. However, when the force of the supporting spring 113 is increased, the life of the thrust bearing 111 between the housing 110 and the rotor 105 is reduced, and the power loss of the engine Eg is increased.
The object of the present invention is to provide a piston type compressor that requires no spring for urging a drive shaft, and an assembly method for the same.
To attain the above-mentioned object, the present invention provides a piston type compressor. The compressor includes a housing and a crank chamber formed in the housing. A drive shaft is rotatably supported by the housing in the crank chamber. The drive shaft has an end surface. A cylinder bore is formed in the housing. A piston is located in the cylinder bore. The piston reciprocates between a top dead position and a bottom dead position. A valve plate is located at an opposite side of the piston from the crank chamber. A swash plate is connected with the piston to change the rotation of the drive shaft to reciprocation of the piston. The swash plate integrally rotates with the drive shaft. A front restriction and a rear restriction are located in the housing and for restricting a movement in the axial direction of the drive shaft. The front restriction restricts the axial movement of the drive shaft in a forward direction. The rear restriction restricts axial movement of the drive shaft in a rear direction. A first clearance is formed between the end surface of the drive shaft and the rear restriction when the movement of the drive shaft is restricted by the front restriction. A second clearance is formed between the piston and the valve plate when the movement of the drive shaft is restricted by the front restriction and when the piston is in the top dead center position. The first clearance is smaller than the second clearance.
The present invention also provides an another piston type compressor. The compressor includes a housing and a crank chamber formed in the housing. A drive shaft is rotatably supported by the housing in the crank chamber. The drive shaft has an end surface. A cylinder bore is formed in the housing. A piston is located in the cylinder bore. The piston reciprocates between a top dead position and a bottom dead position. A valve plate is located at an opposite side of the piston from the crank chamber. A swash plate is connected with the piston to change the rotation of the drive shaft to reciprocation of the piston. The swash plate integrally rotates with the drive shaft. An electromagnetic clutch couples and decouples a power source and the drive shaft. The power source is located outside of the housing. A driven rotary member is supported on the housing. An armature is integrally connected with the drive shaft and facing the rotary member. An electromagnetic coil generates an electromagnetic force to engage the armature with the rotary member. A front restriction and a rear restriction are located in the housing for restricting axial movement of the drive shaft. The front restriction restricts movement of the drive shaft in a forward direction. The rear restriction restricts axial movement of the drive shaft in a rearward direction. A first clearance is formed between the end surface of the drive shaft and the rear restriction when the movement of the drive shaft is restricted by the front restriction, wherein a second clearance is formed between the armature and the driven rotary member when the drive shaft is restricted by the front restriction. The first clearance is smaller than the second clearance.
The present invention also provides an assembly method for piston type compressor. The method comprises locating an end portion of a drive shaft in an accommodation hole of a housing and pressing a restriction member by a first portion of a jig into the accommodation hole. The pressing includes pressing the restriction member axially in the accommodation hole until movement of the drive shaft is restricted by a wall of the housing after a second portion of the jig contacts an end surface of the drive shaft, and the pressing step further includes forming a predetermined clearance between the end surface of the drive shaft and a restriction surface of the restriction member.
The present invention provides another an assembly method for a piston type compressor. The method includes locating an end portion of a drive shaft in an accommodation hole of a housing, and pressing a contact member on the drive shaft by a first portion of a jig. The pressing includes pressing the contact member axially on the drive shaft by the first portion of the jig to a position where a second portion of the jig contacts a wall in which the accommodation hole is formed, and the pressing further includes forming a predetermined clearance between the end surface of the contact member and a valve plate.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.